Transcript Require less time and stimulation to achieve

Dopamine in Male Sexual
Behavior
Elaine M. Hull
The Florida State University
Psychology Department & Neuroscience Program
Neural circuits regulating sexual behavior
NAc
OB
BST
CTF
MPOA
VTA
MeA
Brain Stem
Neural circuits regulating sexual behavior
NAc
OB
BST
CTF
MPOA
VTA
MeA
Brain Stem
Neural circuits regulating sexual behavior
NAc
OB
BST
CTF
MPOA
VTA
MeA
Brain Stem
Neural circuits regulating sexual behavior
NAc
OB
BST
CTF
MPOA
VTA
MeA
Brain Stem
Neural circuits regulating sexual behavior
NAc
OB
BST
CTF
MPOA
VTA
MeA
Brain Stem
Our lab has focused on the medial preoptic area, which contains
A14 periventricular DA neurons. It is the main integrative area
for male sexual behavior in all vertebrate species.
Model for MPOA dopamine’s influence on male sexual behavior
Is dopamine released in the
MPOA during copulation?
Gonadally intact males and T-treated castrates had increased extracellular DA
during pre-exposure to a female and during copulation. Vehicle-treated 1-week
castrates that copulated also showed DA increases, but those that did not
copulate did not show the DA increase.
What elicits the MPOA DA
release?
Large lesions of the amygdala abolished
copulation, which was restored by
apomorphine in the MPOA.
Smaller lesions of the MeA impaired, but
did not abolish mating.
Basal DA levels in the MPOA were normal, but
the DA response to the female was abolished.
Chemical stimulation of the MeA mimicked the
MPOA DA response to a female.
Therefore, normal basal DA in the MPOA is
sufficient for suboptimal copulation. The DA
increase in response to a female facilitates
mating and is mediated by input from the MeA.
• But there are no DA neurons in the MeA.
What elicits the DA increase?
Glutamatergic axons from the
MeA and BNST to MPOA
• Juan Dominguez, my former post-doc,
showed that a few axons from the MeA, and
numerous axons from the BNST, ended in the
MPOA and contained glutamate.
Is glutamate released in the
MPOA before and during mating?
Glutamate % change
Sexual activity increases glutamate in the
MPOA of male rats.
400
**
300
*
200
100
0
BL
PRE
COP
EJAC
PEI
POST
Sample
Using 2 min microdialysis samples
Reverse dialysis of glutamate uptake inhibitors
into the MPOA increased glutamate levels and
facilitated mating.
**
ACSF
UPTKi
Glutamate % change
400
300
200
100
0
BL
UPTKi PRE
COP EJAC
PEI
POST
Samples
EJACULATION
FREQUENCY
5
4
**
EJACULATION
LATENCY (sec)
600
400
300
PEI (sec)
*
500
400
3
200
2
1
0
300
200
100
100
0
0
*
Therefore, glutamate is released
in the MPOA during copulation,
and it facilitates mating.
• Does glutamate also affect MPOA DA levels?
HVA % CHANGE
DA % CHANGE
DOPAC % CHANGE
Exogenous glutamate in the MPOA increased
DA levels, but decreased DOPAC and HVA
Sample (6 min)
Sample (6 min)
Nitric oxide has been reported to
inhibit DA transport and increase
DA levels in the striatum.
• Could NO explain our results?
L-NAME blocked the glutamate-evoked
DA release and the decreases in
DOPAC and HVA.
DOPAC % CHANGE
HVA % CHANGE
DA % CHANGE
Sample (6 min)
Sample (6 min)
Metabolite levels were lower for animals receiving glutamate
alone compared with those receiving glutamate+ L-NAME.
Exogenous glutamate in the MPOA
increased DA levels, but inhibited
metabolites: Role for NO?
POSSIBLE EXPLANATIONS FOR
THIS EFFECT:
1.
Glutamate induces
exocytocis of DA
2.
Glutamate binds NMDA
receptors, which allows for
Ca2+ influx and induces NO
production in NOScontaining cells.
a) Increased NO may inhibit
DA uptake in neighboring
terminals, prolonging
DA’s effects & decreasing
DA catabolism.
b) Increased NO might also
increase extracellular DA
by inducing vesicular
leakage.
MPOA dopamine release during copulation
depends on nitric oxide
L-NAME blocked mating-induced DA release in the MPOA.
Microinjection of L-NAME into the MPOA
impaired copulation in sexually naïve (A)
and experienced (B) males.
A
B
Sexually Experienced Males
1. Show increased preference for being with a
receptive female.
Sexually Experienced Males
1. Increased preference for being with a receptive
female.
2. Require less time and stimulation to achieve
ejaculation.
Sexually Experienced Males
1. Increased preference for being with a receptive
female.
2. Require less time and stimulation to achieve
ejaculation.
3. Require less time to resume copulation after
ejaculating.
Sexually Experienced Males
1. Increased preference for being with a receptive
female.
2. Require less time and stimulation to achieve
ejaculation.
3. Require less time to resume copulation after
ejaculating.
4. Are more resistant to sexual impairments due to
castration, brain damage, or stress.
Sexually Experienced Males
1. Increased preference for being with a receptive
female
2. Require less time and stimulation to achieve
ejaculation
3. Require less time to resume copulation after
ejaculating
4. Are more resistant to sexual impairments due to
castration, brain damage, or stress
Is the MPOA implicated?
Stronger Activation of the MPOA in
Sexually Experienced Males
First Experience
Repeated Experience
Sexually experienced males had more Fos-ir in the
MPOA resulting from mating to one ejaculation, than
did naïve males that mated for the first time.
Does NOS in the MPOA contribute to
exposure-induced enhancement of mating?
L-NAME administration before each of seven non-copulatory exposures to an
estrous female blocked exposure-induced enhancements on the drug-free test
day. (Preliminary data suggest that a D1 antagonist has similar effects.)
Sexual experience increases
NOS-ir in the MPOA of male
rats
% NOS w/NR1
100
Percentage
NOS
75
NMDAR1
50
25
0
NNS
NS
ENS
ES
Total NOS
80
*
60
*
*
# Cells
40
20
0
NNS
NS
ENS
ES
Nearly all cells containing NOS also contained NMDA receptors.
Sexual experience increased the number of NOS-ir cells in MPOA.
Overlay
Sexual experience increases NOS protein
concentration in the MPOA of male rats
Sexually Naïve
and Not Mated
(NC)
Sexually
Experienced
and Not Mated
(EC)
Sexually Naïve
and Mated
(NM)
*
MEAN DENSITY
(PIXELS)
150
*
100
*
50
0
NC
NM
EC
EM
Sexually
Experienced
and Mated
(EM)
A major means of activating NOS is via
NMDA glutamate receptors.
Does an NMDA antagonist in the
MPOA also impair sexual sensitization?
Blocking NMDA receptors in the MPOA
impaired sexual sensitization.
Microinjecting MK-801 before each
noncopulatory exposures to an
estrous female impaired exposureinduced enhancements of:
16
14
MOUNTS
1. number of mounts
12
10
8
6
4
2
0
*
Saline
MK801
Naive
Blocking NMDA receptors in the MPOA
impaired sexual sensitization.
1. number of mounts
2. number of intromissions
INTROMISSIONS
Microinjecting MK-801 prior to repeated
noncopulatory exposures to an
estrous female impaired experienceinduced enhancements on:
18
16
14
12
10
8
6
4
2
0
Saline
MK801
Naive
*
Blocking NMDA receptors in the MPOA
impaired sexual sensitization.
Microinjecting MK-801 prior to repeated
noncopulatory exposures to an
estrous female impaired experienceinduced enhancements on:
1. number of mounts
2. number of intromissions
3. number of ejaculations
EJACULATIONS
2.5
2
1.5
Saline
MK801
Naive
1
0.5
0
*
• What intracellular messenger
mediates NO’s effects?
Cyclic GMP mediates NO’s facilitation
of DA release in the MPOA
Inhibition of guanylyl cyclase blocked effects of the NO donor
(sodium nitroprusside).
Cyclic GMP mediates NO’s facilitation
of DA release in the MPOA
Inhibition of NOS did not affect facilitation by cGMP analog,
because cGMP is downstream of NOS.
Summary
Sexual stimulation
NMDAr
Glutamate
NOS
Dopamine
Summary
Sexual stimulation
NMDAr
Glutamate
NOS
Dopamine
NO
Summary
Sexual stimulation
NMDAr
Glutamate
NOS
(Higher NOS
w/ experience)
Dopamine
NO
Postscript: Orexin/hypocretin increases
mesolimbic DA activity and facilitates
copulation
Copulation increased Fosir in orexin-containing
neurons of perifornical LH.
Double-labeled cells in
Non-copulating males
Double-labeled cells
in copulating males
Castration
decreased
orexincontaining
cells; E2
restored them.
Orexin (.014 nmol) in the
VTA increased firing rates
of DA neurons.
Orexin (1.4 nmol) in the VTA
increased cells per track,
but not firing rates.
Orexin (140 nmol) in the
VTA decreased cells per
track, probably due to
depolarization block, an
effect reversed by
autoreceptor stimulation by
systemic apomorphine.
Red orexin-containing axons end near green THcontaining neurons that are activated (Fos-ir, black) by
copulation.
• Estrogen receptor-containing cells in the MPOA, BNST, and
LHA  orexin-containing cells in the LHA. Axons from those
cells depolarize DA-ergic cells in the VTA and, perhaps, the
MPOA. Microinjection of orexin into the MPOA facilitates male
sexual behavior (Gulia et al., 2003). 5-HT is released in the LHA at
the time of ejaculation and inhibits mating. It also decreases DA
release in the NAc (Lorrain et al., 1999) and hyperpolarizes orexin
neurons (Li et al., 2002).
Acknowledgments
Juan Dominguez, Ph.D
John Muschamp, Ph.D
Mario Gil
Satoru Sato, Ph.D
Gwen Lagoda
Anna Vigdorchik
Daniel Lorrain, Ph.D
Harvey Rattus
Lucy Lumley, Ph.D
Former and Present Lab Members:
Bradley Lown, Ph.D
Linda Rosselli-Austin, Ph.D
Rosemary D’Agostino, Ph.D
Deborah Kleese Edelstein, Ph.D
Mary Solanto, Ph.D
Richard Thomas, Ph.D
J. Ken Nishita, Ph.D
Daniel Bitran, Ph.D
Elizabeth A. Pehek, Ph.D
Linda C. Band, Ph.D
Terrence Bazzett, Ph.D
Vincent P. Markowski, Ph.D
Robert C. Eaton, Ph.D
Jason Moses, Ph.D
Leslie Matuszewich, Ph.D
Jianfang Du, Ph.D
Susan K. Putnam, Ph.D
Jon V. Riolo, Ph.D
Katie Grausam
K02-MH001714
R01-MH040826
SNP and 8-Br-cGMP increase DA levels in
the MPOA of DHT-treated castrates.
However, SNP was somewhat more effective.
Only SNP increased DOPAC in DHT-Treated
Castrates
Only SNP into the MPOA facilitated sexual
behavior in DHT treated castrates
100.00
Percent that Displayed Mounts
90.00
80.00
*
PERCENT
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
Control
8-Br-cGMP
SNP
Only SNP into the MPOA facilitates sexual
behavior in DHT treated castrates
100.00
Percent that Displayed Intromissions
90.00
80.00
PERCENT
70.00
60.00
*
50.00
40.00
30.00
20.00
10.00
0.00
Control
8-Br-cGMP
SNP
Only SNP into the MPOA facilitates sexual
behavior in DHT treated castrates
100.00
Percent that Displayed Ejaculations
90.00
80.00
PERCENT
70.00
60.00
*
50.00
40.00
30.00
20.00
10.00
0.00
Control
8-Br-cGMP
SNP
400
**
300
*
200
100
0
BL
PRE
COP
EJAC
Sample
PEI
POST
Glutamate % decrease
Glutamate % change
Magnitude of decrease in glutamate after
ejaculation correlates with post-ejaculatory
interval.
600
500
400
300
200
100
0
100
200
300
400
PEI (Sec)
500
600
Blocking D1 Receptors Attenuated
Activation of MPOA During Initial
Experience
Vehicle
D1 Antagonist
Males receiving a D1 antagonist had less Fos-ir in
the MPOA after their first sexual experience, than
did males receiving vehicle.